This invention relates to a synchronous machine. More particularly, this invention relates to a rotor lamination for a multi-pole permanent magnet synchronous machine.
A synchronous motor is a synchronous machine which is characterized by its ability to run at a constant speed which is independent of motor load. The constant speed of the motor is dependent upon the frequency of the motor current and the number of motor poles. Therefore, for a given frequency current, the motors constant speed is dependent upon the number of motor poles.
For many applications the frequency of the motor current is 60 Hz which corresponds to the frequency of the power supplied by utilities. (50 Hz for many European countries.) Synchronous motors are manufactured having a number of poles corresponding to a desired constant operating speed. For example, at 60 Hz a 2 pole machine will operate at 3600 rpm, a 4 pole machine at 1800 rpm and an 8 pole machine at 900 rpm. To obtain very specialized speeds, the frequency and pole number can be varied. For example, to obtain a speed of 2040 rpm 68 Hz current and 4 poles could be used.
Referring to the drawings, FIG. 1 illustrates a rotor lamination for a 2 pole permanent magnet motor and FIG. 2 illustrates a rotor lamination for a 4 pole machine. Presently, different rotor laminations are used to produce permanent magnet motors having differing numbers of poles. As a result, different tooling is required to produce the different rotor laminations for motors having differing numbers of poles. Thus, for a manufacturer producing 2, 4 and 8 pole motors, three different types of lamination producing dies are required.
Accordingly, it would be desirable to have a rotor lamination which could be used universally in 2, 4 and 8 pole machines.